This invention relates to hydraulically-operated oscillatory devices, and particularly but not exclusively to percussive devices of the type embodying a reciprocatory piston/striker and cylinder arrangement with a sequence valve operated by a pilot port controlled by the piston/striker itself to limit the piston stroke.
In our U.S. Pat. No. 3,887,019 we have described such a device which, for efficient and satisfactory operation, has to be matched to the hydraulic power supply in terms of pressure and volume flow. There is a requirement for percussive devices, for example a light portable hammer, which can selectively be operated with either short high-speed strokes of low energy or long and relatively low-speed strokes of relatively high energy, but the problem is to design such a device which will be satisfactorily matched to the same power source in each operating condition.